The present application claims priority to Japanese Application No. P10-328512 filed Nov. 18, 1998 which application is incorporated herein by reference to the extent permitted by law.
1. Field of the Invention
The present invention relates to a nonaqueous electrolyte battery incorporating a casing constituted by a laminate film in which a battery element is accommodated. More particularly, the present invention relates to improvement in a volume energy density of a gel electrolyte battery, a solid electrolyte battery or the like.
2. Description of the Related Art
In recent years, a multiplicity of portable electronic apparatuses including camcoders, portable telephones and portable computers have come on the market. An attempt has been made to reduce the size and weight of the foregoing electronic apparatuses. As the portable power sources for the foregoing electronic apparatuses, batteries, in particular, secondary batteries, and more particularly, nonaqueous-electrolyte secondary batteries (so-called xe2x80x9clithium ion batteriesxe2x80x9d) have energetically researched and developed to reduce the thickness of the battery and realize a foldable structure.
As the electrolyte for the shape-variable battery, solidified electrolytic solution has energetically been studied. In particular, attention is being given to a polymer solid electrolyte lithium salt is dissolved in a gel electrolyte, which is a solid electrolyte containing a plasticizer, or a polymer.
On the other hand, the merits of the foregoing battery, which are small thickness and light weight, are attempted to be used. Therefore, a variety of batteries have been studied which have an encapsulating structure which uses a plastic film or a laminate film constituted by bonding a plastic film and a metal sheet to each other.
For example, a secondary battery must have a control circuit which controls charge/discharge and which is disposed in the vicinity of the battery. Therefore, a structure is required with which the volume efficiency can be improved if the foregoing charge/discharge circuit is mounted.
Moreover, the battery having the above-mentioned structure must have a variety of characteristics as the battery investigated to cause the overall body of the battery including the control circuit to have impact resistance, improve the efficiency when the volume energy density is defined with the outer size of the battery constituted by the laminate film and improve heat radiating characteristic to elongate lifetime against charge/discharge cycles which is one of performance factors when the battery is operated.
In view of the foregoing, an object of the present invention is to provide a nonaqueous electrolyte battery exhibiting an excellent volume efficiency even if a control circuit is mounted thereon.
Another object of the present invention is to provide a nonaqueous electrolyte battery exhibiting excellent impact resistance and a heat radiating characteristic and having a long lifetime against charge/discharge cycles which is a performance factor when the battery is used.
Another object of the present invention is to provide a nonaqueous electrolyte battery exhibiting excellent producibility.
To achieve the foregoing objects, according to one aspect of the present invention, there is provided a nonaqueous electrolyte battery incorporating a casing constituted by a laminate film in which a battery element is accommodated and encapsulate by welding and electrode-terminal leads electrically conducted with electrodes are exposed to the outside portion of the casing such that the electrode-terminal leads are sandwiched by a welded portion, the nonaqueous electrolyte battery comprising: a control circuit for the nonaqueous electrolyte battery mounted on the welded portion of the casing.
The term xe2x80x9cweldedxe2x80x9d as used throughout the text means the same as and is interchangeable with the term xe2x80x9cheat sealing.xe2x80x9d
Since the control circuit of the battery is mounted on the welded portion, spaces in the battery in which the battery element is not present can effectively be used. As a result, the volume efficiency can considerably be improved.
The basic concept of the present invention is as described above. Moreover, the present invention is structured to raise the volume energy density of the outer size of the battery including the control circuit for the battery. Thus, excellent impact resistance is attempted to be realized. Therefore, a portion of the welded portion except for the portion in which the electrode-terminal leads are sandwiched by the laminate film and which is welded is folded one or more times toward the side ends of the battery to have a width smaller than the thickness (the shortest length of the battery is defined to be a xe2x80x9cthickness of the batteryxe2x80x9d) of the battery. Thus, the size in the direction of the thickness of the battery is minimized. Thus, the foregoing folded portion protects the overall body of the battery including the battery.
To improve the heat radiating characteristic, the portions folded toward the side ends of the battery are not bonded, that is, folded so as to enlarge the surface area.
To improve impact resistance, the portions are folded toward the side ends of the battery with a curvature.
Other objects, features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.